This study will evaluate the effects of hormone replacement therapy on patients with Turner syndrome (TS)-a genetic disorder in females in which part or all of one X chromosome is missing. Most girls and women with TS have underdeveloped ovaries-the female reproductive organs that produce the female sex hormones estrogen and progesterone, and smaller amounts of the male sex hormone, testosterone. These hormones affect muscle and bone strength, sex drive, energy, and an overall sense of well being. Estrogen may also play a role in memory and mood and have a protective effect against heart disease. Women with TS have a much higher risk of developing osteoporosis (loss of bone density), high blood pressure, high cholesterol and diabetes than women without this disorder.